X i improvement



. D. HOFFMAN.

Tripod-Head for Surveying Instruments. No. 197,369.

Patented Nov. 20, i877.

l I n WITNESSES I' NVEVNTOR ATTORN EY 'T0 all-.whomtimer/90mm! 1 r' B it"known" that Ii; DANIEL* HOFFMAN;- Of renacer-)hannekeeountyofrhiiadeiphiaana State ofV Pennsylvania, havefinvent'ed alnew and; .valuable I'Impmvement in Tripod-Heads; and I do hereby declare that the following is a full, clear, andexactdescriptionfof-theconstruction and oprationof "ther same, reference being had to the annexed drawings, making a part of this specication, and to the letters and figures oi' reference marked thereon.

Figure l of the drawings is a representa` tion of a top view of my improvedatripod-head, and Fig. 2 is avertical central sectionof the same.

This invention has relation to improvements in tripod-heads for transits, levels, theodolites, and other instruments for surveying,engineer ing, and astronomical purposes. f The object of the invention is to devi-se a tripod-head ofsuch a construction that itmay be leveled with absolute accuracyand expedition, and may be adjusted horizontally for bringing the center of the instrument over a fixed point on lthe ground, whatever be the nature of the same or its inclination.

" The nature of the invention will be readily yperceived from the following description, and

pointed out in theclaims appended thereto.

In the annexed drawings, the letter A designates 4the base-plate kof my improved tripodhead, having a large central circular opening,

j a, and 'a ilange, a', upon. its under side, provided with a coarse screw-thread upon its inner.:faceby means of which'the whole head is i j secured to the tripod.- i

B represents the carrier-plate, upon which the upper part of the head is supported. This plate has acentral opening, b,- of circular form, of

, less diameter than the opening aiof plate A. C represents a socket-plate having a short central neck, c, in which the concave bearingsurface c ofthe lowerball-andsocket joint isformed. This plate is passed'from below inside of the iiange a, and its neck thrust through the openings a b of the base-plate 'and of the carrier-plate,

respectively.- The diameter ofthe neckc and of v the orifice b of the plate B are the same, and the neck fits snuglyiu theV said orifice. The ball D ofthe lower socket-joint is passed up through 4 `the neck, and its` projecting screw-threaded jFoRjslj-nvrvme l-NsTRuMEINTs 369, dated November 240,V plicationiiled i I@mi @through the 'leveling-saw 1pm@ E. n

isthen screwedlinto the lower end 'of the neck '0, projecting downward from th ,plate F, to which theinstrument is directl attached.I

" The leveling-screwplateE-ha" a-large'central opening, j, and .onitsupperface is provi'dedwithfa convex'aniiult i`g, which is re,- reeived inland accurately 'iits n concavejsocket', 'h',upo1'i the underside of l the'pl'ate Llaioresa'id. When the end d is screwed into-the neck c aforesaid, the parts of the tripod-head are coupled together. u

The convex annulus g and the socket h form the upper ball-and-socket joint of my improved head for tripods, and their curved surfaces and those of the lower ball-and-socket joint are concentric 5 consequently, while the levelingscrew plate is motionless, the instrument-plate F has free universal movement upon'the lower ball-and-socket joint c D, in the ball of which the 'centers oi' the curved surfaces of both the upper and .lower jointsare coincident. The,

neck e of the instrument-plate and that of the ball, as aforesaid, are connected together, and the axial line of the former, if extended, would pass through the center of the latter; consequently, when the said plate is level and the instrument properly secured thereon, thecenter of latter must be in line with the longitudinal axis ofthe neck and the center of the ball, and the plummet-line in the vertical prolongation of the said axis. i

By sliding the carrier-plate A horizontally the plummet may be brought directly over the fixed point on the ground with great accuracy and expedition, thus bringing the center of the i instrument and the said iixed point in the same -vertical line.

By setting up the leveling-screws G the level thus obtained and the adjustment of the center of the instrument over the iixed point on the ground may be preserved for any length of' time, whatever be the nature of the ground.

',These leveling-screws extend through long screw-threaded nuts I, rigidly secured to the plateE,exactlyatrightangles thereto,andtheir lower ends bear upon the plate B, as shown; consequently they are notliable to become jammed in their bearings, to lose their posi= tion with reference to plate E, nor to interfere with the base-plate. .y Y

I operate the head as follows to obtain a level position for the instrument and bring its center in the vertical line of the fixed point on the ground: I loosen any two of the levelingscrews which may be convenient, (about one half-turn will be suicient,) thereby letting down plate C suiciently to clear it from the base-plate, and permitting the carrier-plate B to be shifted in any direction horizontally, carrying the leveling-plate, the upper and lower ball-and-socket j oints, and the instrument-plate with it, until the instrument on the head is centered over the fixed point on the ground. This being accomplished, I level the instrument approximately by hand, and exactly by setting up the two levelingscrews aforesaid, as may be requisite. This causes the ball and sockets to bind tightly upon each, and produces the desired result.

What I claim as new, and desire to secure by Letters Patent, is-

1. The combination, with the plate A, hav

ing central opening a, and the plate C, having v the socket c' extending through said opening,

of the ball D, having threaded; neck d, the lei cling-screw plate E, having balll,g,fand theinstrument-plate F, having neck c and socket h, substantially as specified.

2. The combination, with the base-plate A, having central opening a,and.tl1lesocketplate C, having neck c, of the carrying-plate B,hav ing aperture b, fitting said neck, and the leveling mechanism of a tripod-head, substantially as speciiied.

3. A tripod-head having a ball-and-socket v joint for the base-plate, in combination with the instrument-plate F, having a spherical bearing, g h, concentric with said ball-and-socket joint, and leveling-plate E, substantially as speciiied. y, A

In testimony that I claim theabove I have hereunto subscribed my namein vthe presence of two witnesses.

DANIEL HOFFMAN.

Witnesses: l 4

ALLEN H. GANGEWR, i' H. C. BRICK. y

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